Interoperability between symmetric and asymmetric evpn irb modes

ABSTRACT

A system and method are disclosed for enabling interoperability between asymmetric and symmetric Integrated Routing and Bridging (IRB) modes. A system is configured to receive a route advertisement, examine the label fields of the route advertisement, and determine whether Layer 2 or Layer 3 information is conveyed. The system is further configured to build a route advertisement to advertise to a second device based on whether Layer 2 or Layer 3 information is conveyed in the first route advertisement.

TECHNICAL FIELD

The subject matter of this disclosure relates in general to the field ofcomputer networks, and more specifically improving the accuracy andefficiency of forwarding tenant traffic between devices supportingdifferent modes.

BACKGROUND

A network is a group of interconnected computing devices that canexchange data. An Ethernet Virtual Private Network (EVPN) may be used toextend and optimize remote Layer 2 (L2) and Layer 3 (L3) customernetworks through an intermediate network. A network endpoint is aphysical or virtual device connected to a computer network. An endpointoffers information, services, and applications to users or other nodesconnected to the network. An endpoint is a node that is assigned aunique L2 network route, such as Media Access Control (MAC) route, and aunique L3 network route, such as an Internet Protocol (IP) route.

A tenant needing Integrated Routing and Bridging (IRB) services on aProvider Edge (PE) device requires an IP Virtual Routing and Forwarding(IP-VRF) table and a MAC Virtual Routing and Forwarding table (MAC-VRF).A MAC-VRF can have Bridge Tables (BTs) that are connected to an IP-VRFvia an IRB interface. There are as many BTs as there are subnets, for agiven tenant, and thus there are also as many IRB interfaces between thetenant IP-VRF and the associated BTs. IP-VRF is identified by itscorresponding route target and route distinguisher and MAC-VRF is alsoidentified by its corresponding route target and route distinguisher.

There are two models to accomplish inter-subnet forwarding withEVPN—asymmetric IRB and symmetric IRB modes. In symmetric IRB mode, theinter-subnet forwarding between two PE devices is done between theirassociated IP-VRFs. In asymmetric IRB mode, the inter-subnet forwardingbetween two PE devices is done between their MAC-VRFs and BTs. Differentvendors use different modes and once a network is built using one mode,the other mode cannot be used in the same network. With symmetric IRB,all traffic egressing and returning from a VXLAN Tunnel Endpoint (VTEP)uses the same VNI and the bridge-route-route-bridge sequence offersflexibility for large-scale multitenant deployments. With respect toasymmetric IRB, there are differences concerning which VNI the IPpackets travel through due to the differences between where and how therouting lookups are done. These differences cannot be reconciled unlessthe configuration is changed. Thus, it is advantageous for products tobe placed in deployments that work with either of these modes.

BRIEF DESCRIPTION OF THE FIGURES

In order to describe the manner in which the above-recited and otheradvantages and features of the disclosure can be obtained, a moreparticular description of the principles briefly described above will berendered by reference to specific embodiments that are illustrated inthe appended drawings. Understanding that these drawings depict onlyembodiments of the disclosure and are not therefore to be considered tobe limiting of its scope, the principles herein are described andexplained with additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 is a simplified schematic block diagram illustrating a networkenvironment configured to implement the method for enablinginteroperability between asymmetric and symmetric modes, in accordancewith the various techniques described in this disclosure;

FIG. 2 is a simplified schematic block diagram illustrating a networkdevice that implements techniques to improve inter-subnet forwarding inan EVPN when delivering traffic to nodes that support different IRBfunctionality, in accordance with the various techniques described inthis disclosure;

FIG. 3A is a simplified schematic block diagram illustrating an exampleof a PE network device, in accordance with the various techniquesdescribed in this disclosure;

FIG. 3B is a simplified schematic block diagram illustrating an exampleof a gateway PE, in accordance with the various techniques described inthis disclosure;

FIG. 4 is a process flow diagram illustrating the method performed bythe hybrid IRB node of providing inter-subnet connectivity regardless ofwhether the egress PE is a symmetric IRB PE or an asymmetric IRB PE, inaccordance with the various techniques described in this disclosure;

FIG. 5A is a simplified schematic block diagram illustrating theoperation of a symmetric IRB PE, in accordance with the varioustechniques described in this disclosure;

FIG. 5B is a simplified schematic block diagram illustrating theoperation of an asymmetric IRB PE, in accordance with the varioustechniques described in this disclosure.

DESCRIPTION OF EXAMPLE EMBODIMENTS

The detailed description set forth below is intended as a description ofvarious configurations of embodiments and is not intended to representthe only configurations in which the subject matter of this disclosurecan be practiced. The appended drawings are incorporated herein andconstitute a part of the detailed description. The detailed descriptionincludes specific details for the purpose of providing a more thoroughunderstanding of the subject matter of this disclosure. However, it willbe clear and apparent that the subject matter of this disclosure is notlimited to the specific details set forth herein and may be practicedwithout these details. In some instances, structures and components areshown in block diagram form in order to avoid obscuring the concepts ofthe subject matter of this disclosure.

Overview

A system and method are disclosed for enabling interoperability betweenasymmetric and symmetric Integrated Routing and Bridging (IRB) modes. Ahybrid IRB mode is introduced, in which the Provider Edge (PE) devicedetects the IRB operation it receives and deploys an IRB PE that behavesthe same way. The function of the PE device is to forward trafficbetween receivers. When a symmetric formatted route is received from asymmetric IRB PE, the hybrid PE device is configured to process the EVPNRoute Type 2's (MAC/IP Advertisement Route) as follows: Media AccessControl (MAC) portion into the MAC-VRF and its respective Bridge-Table(BT) and Internet Protocol (IP) portion into the IP-VRF and itsrespective routing table. When an asymmetric formatted route is receivedfrom an asymmetric IRB PE, the hybrid PE device is configured to processthe MAC/IP Advertisement Route as follows: MAC portion into the MAC-VRFand its respective BT and MAC plus IP portion combined installed in thelocal ARP table pointing to the asymmetric IRB PE. As a result, thereceiving PE device directs inter-subnet traffic forwarding based uponthe advertisement it receives and facilitates interoperability betweenimplementations with symmetric IRB and implementations with asymmetricIRB. This method is accomplished with no change to the control plane orconfiguration of the IRB nodes. This technology allows manufacturers tosell one type of device that will be able to work with both symmetricand asymmetric IRB modes.

Example Embodiments

Various embodiments of the disclosure are discussed in detail below.While specific implementations are discussed, it should be understoodthat this is done for illustrative purposes only. A person skilled inthe relevant art will recognize that other components and configurationsmay be used without departing from the spirit and scope of thedisclosure.

Various embodiments relate to a hybrid PE node that receives an MAC/IPAdvertisement Route as an egress switch. The hybrid PE node receives aMAC/IP Route advertisement of an IP network and acts as hybrid IRB node.The hybrid IRB node creates and advertises an EVPN Route Type 5 (IPPrefix Route) towards the Symmetric IRB nodes, and forwards trafficproviding seamless interoperability between different IRB modes andinter-subnet connectivity.

FIG. 1 is a simplified schematic block diagram illustrating a networkenvironment 100 configured to implement the method for enablinginteroperability between asymmetric and symmetric IRB modes, inaccordance with the various techniques described in this disclosure. Thenetwork environment 100 includes a set of interconnected networkingelements in a leaf and spine architecture. Each spine switch/router 104in the network is connected to a leaf switch/router 106 and the leafswitch/router 106 is connected to one or more servers 108. The serverscan each host Virtual Machine (VM) 110 or host one or more virtualendpoints. The one or more servers 108 and one or more VMs 110 can bereferred to as the host facing interface.

The network environment 100 may be a Multiprotocol Label Switching(MPLS)/Internet Protocol (IP) network for intra-subnet connectivityamong endpoints that can be physical or virtual. FIG. 1 and otherexamples presented herein describe the use of Ethernet Virtual PrivateNetwork (EVPN) for exchanging the endpoint MAC and IP routes. In certainexamples, the overlay network 102 employs an EVPN-based IRB. The overlaynetwork 102 is referred to as an EVPN IRB network. The leafswitch/router 106 can be called an “edge device” and it is where the IRBfunction is hosted on.

The EVPN IRB network provides inter-subnet forwarding as well as theability of a VM 110 to migrate from one server 108 to another within thesame or different network without change to its existing MAC and IPaddress. The leaf switch/router 106 also performs Virtual ExtensibleLocal Area Network (VXLAN) encapsulation and decapsulation on framescoming from and going to VM 110 running on the attached host servers108. VXLAN is a L2 overlay scheme on a L3 network. The encapsulationscan be label-based encapsulations, such as MPLS, SR-MPLS or IP-basedencapsulations such as VXLAN, SRv6, GENEVE, GPE.

In an embodiment, devices that support VXLANs are called virtual tunnelendpoints (VTEPs). VTEPs can be end hosts or network switches orrouters. VTEPs encapsulate VXLAN traffic and de-encapsulate that trafficwhen it leaves the VXLAN tunnel. To encapsulate an Ethernet frame, VTEPsadd a number of fields, including a VXLAN header that includes a 24-bitfield, which is called the VXLAN network identifier (VNI). For example,border leaf router encapsulates and decapsulates frames for VM 110running on one of the servers 108.

FIG. 2 is an illustration showing a network device that implementstechniques to improve inter-subnet forwarding in an EVPN when deliveringtraffic to nodes that support different IRB functionality in accordancewith techniques described in this disclosure. One or more of the PErouters 210 may implement IRB, such that each PE router 210 is able toprovide both L3 routing and L2 switching between different L2 domainswithin a single router. An IRB includes a routing interface for an IRBsubnet as well as a Bridge Domain (BD) and in turn facilitatessimultaneous L2 bridging and L3 routing from the BD. One or more IRBinterfaces may be used to locally route inter-subnet traffic. When a PEdevice 210 with IRB capability receives tenant traffic, it can locallybridge the intra-subnet traffic and locally route the inter-subnettraffic on a packet by packet basis.

Each of the PE routers 210 may implement Virtual Routing Functionality(VRF), where each PE router 210 includes one or more VRF instances. EachVRF instance in a given router may represent a logically separaterouting and forwarding instance. This includes both a correspondingrouting table and forwarding information in the control plane andforwarding plane for the router. PE 210 is configured with IRB having aBD that provides L2 reachability to L3 subnet that includes endpoints212. In some embodiments, Customer Edge (CE) router 208 can be a Layer-2only PE while PE 210 is a Layer-2/Layer-3 PE hosting the IRB function.PE routers 210 locally learn MAC addresses for customer endpoints. PErouter 210 may receive an IP packet for routing using IRB, the IP packetsourced by endpoint 212 and destined for endpoint 212. The IP packet mayhave a destination MAC address that corresponds to the IRB interface MACaddress. PE router 210 determines the IP packet is to be inter-subnetrouted and performs an IP lookup in VRF.

In some cases, PE routers 210 may learn the IP addresses associated withrespective MAC addresses in the control plane between the CEs 208 andthe PE routers 210. PE devices 210 provide customer equipment associatedwith customer networks 204 with access to intermediate networks 202. PEs210 coupled to CE routers 208 of customer networks 204 via attachmentcircuits. An intermediate network 202 can be a service provider network,which represents a publicly accessible computer network that is ownedand operated by a service provider.

A type of business class data service offered by service providernetwork 12 includes EVPN 206. EVPN 206 is a service that provides a formof L2 and L3 connectivity across an intermediate network, such asservice provider network, to interconnect an L2 customer network with anL3 customer network that are usually located in two different geographicareas.

In the example of FIG. 2, when providing the EVPN 206 service tocustomer networks, PEs 210 and CEs 208 typically perform MAC addresslearning to efficiently forward L2 network communications in system. AsPEs 210 and CEs 208 forward Ethernet frames, the routers learn L2information, including MAC addressing information for customer equipmentwithin the network. PEs 210 and CEs 208 typically store the MACaddressing information in MAC tables associated with respectiveinterfaces.

As PEs 210 learn the MAC address for customer equipment reachablethrough local attachment circuits, the PEs 210 utilize routeadvertisements of a L3 routing protocol, such as a Border GatewayProtocol (BGP), to share the learned MAC addresses and to provide anindication that the MAC addresses are reachable through the particularPE that is issuing the route advertisement. In the EVPN implemented insystem, each of PEs advertises the locally learned MAC addresses toother PEs using a BGP route advertisement, referred to herein as “EVPNMAC advertisement route.”

As further described below, an EVPN MAC advertisement route typicallyspecifies an individual MAC address of customer equipment along withadditional forwarding information, such as a route descriptor, routetarget, L2 segment identifier, MPLS label, etc. In EVPN, PEs advertisethe MAC addresses learned from the CEs that are connected to them, alongwith an MPLS label, to other PEs in the control plane usingMultiprotocol BGP. PEs 210 may perform both local learning and remotelearning of MAC addresses. Each of PEs 210 utilizes EVPN MACadvertisement route specifying the MAC addresses learned by other PErouters 210 to determine how to forward L2 communications to MACaddresses that belong to CEs 208 connected to other PEs 210.

FIG. 3A illustrates an example of a PE network device 300, in accordancewith the techniques described in this disclosure. PE 300 includes acontrol unit 302 that includes a routing engine 304 coupled to aforwarding engine 318. Control unit 302 may be implemented solely insoftware, or hardware, or may be implemented as a combination ofsoftware, hardware, or firmware. Control unit 302 may include one ormore processors which execute software instructions. In that case, thevarious software modules of control unit 302 may comprise executableinstructions stored on a computer-readable medium, such as computermemory or hard disk.

Routing engine 304 provides an operating environment for variousprotocols that execute at different layers of a network stack. Networkprotocols include routing protocols, such as BGP. PE 300 includes one ormore interface cards (IFC) 320 that receive packets via incoming links322 and send packets via outbound links 324. Incoming links 322 andoutbound links 324 may represent physical interfaces, logicalinterfaces, or some combination thereof. Control unit 302 determinesroutes of received packets and forwards the though the IFC 320.

Forwarding engines 318 represent hardware and logic functions thatprovide high-speed forwarding of network traffic. In general, when PE300 receives a packet via one of incoming links 322, one of forwardingengines identifies an associated next hop for the IP packet bytraversing the programmed forwarding information 326 based oninformation within the packet. The ingress forwarding engine or adifferent egress forwarding engine will forward the packet on one ofoutbound links 324 mapped to the corresponding next hop.

Forwarding engine 318 receives IP packets on incoming links that aredestined for one of the PE routers 300 in the EVPN. Forwarding engine318 determines whether the destination customer MAC address of the IPpackets is included in the one of MAC tables associated with the EVPN.If the MAC address is included in the one of MAC tables, then PEforwards the IP packets to the destination PE router based on forwardinginformation associated with the EVPN. If the MAC address is not includedin the one of MAC tables, PE floods the IP packets to all of the PErouters based on forwarding information associated with the EVPN.

VRF 310 is configured with a routing interface of IRB 314, the logicalinterfaces for which are configured to forward information of forwardingengine. Each IRB 314 interface provides a L3 interface for a L2 subnet,and VRF 310 configures forwarding information to bridge traffic betweenthe domains. Routing information may configure IRBs 314 using routinginformation provided by VRF 310.

An ARP (Address Resolution Protocol) lookup is done to identify host MACaddress and adds an Ethernet encapsulation in the header of an IP packetif a valid MAC address is found. A lookup function verifies whether ornot an ARP entry exists in the ARP table 316. ARP tables 316 represent adata structure storing a plurality of address resolution entries eachassociating an L2 addresses with a corresponding L3 address that hasbeen learned by PE router 300 for a customer device.

FIG. 3B is a simplified schematic block diagram illustrating an exampleof a gateway PE, in accordance with the various techniques described inthis disclosure. Each PE router maintains a number of separateforwarding tables, including the VPN Routing and Forwarding tables(VRFs). Every PE attachment circuit 328 is associated, by configuration,with one or more VRFs. In the simplest case, a PE attachment circuit 328is associated with exactly one VRF. When an IP packet is received over aparticular attachment circuit 328, its destination IP address is lookedup in the associated VRF. The result of that lookup determines how toroute the packet.

A tenant needing IRB services on a PE, requires an IP-VRF 330 along withone or more MAC-VRFs 332. A MAC-VRF 332 can consist of one or moreBridge Tables (BTs) where each BT corresponds to a Broadcast Domain (BD)334. If service interfaces for an EVPN PE are configured in VLAN-Basedmode then there is only a single BT per MAC-VRF 332. If serviceinterfaces for an EVPN PE are configured in VLAN-Aware Bundle mode thenthere are several BTs per MAC-VRF 332. Each BT is connected to a IP-VRF330 via a L3 interface called IRB interface 334. For a given tenant,there are as many BTs as there are subnets and thus there are also asmany IRB interfaces 334 between the tenant IP-VRF 330 and the associatedBTs as shown in FIG. 3B. PE routers use BGP 336 to cause VPN routes tobe distributed to each other. MPLS or IP tunnel 338 transportsMPLS-label and payload from one PE to another.

FIG. 4 illustrates a process flow diagram illustrating the methodperformed by the hybrid IRB node of providing inter-subnet connectivityregardless of whether the egress PE is a symmetric IRB PE or anasymmetric IRB PE. Inter-subnet communication is when a Tenant System(TS) wants to communicate with another TS belonging to a differentsubnet connected to the same PE node. Operation 400 is described withrespect to PE 300 of FIG. 3. Routing engine 304 analyzes routinginformation 306 and generates forwarding information 326, which may bemaintained in one or more tables.

The hybrid IRB node can be a receiving PE that receives EVPN MAC/IPAdvertisement Route with MAC VRF route target 402. The receiving PElearns the MAC and IP addresses of a TS via an ARP request. To advertisenew routes, PE determines if the MPLS label for the first routeadvertisement includes IP-VRF attributes 404. If IP-VRF attributes arepresent, indicating that it is a symmetrically formatted route, the PEinstalls the MPLS Label2 field in the forwarding path to identify thecorresponding IP-VRF 414. The PE adds the IP route to the IP-VRF table414 and the MAC address to the MAC-VRF table 416. By doing this, itimports L2 information in BD that maps to BD route target and L3information in route advertisement is also imported in VRF that maps toL3 route target 418. Then it programs a MAC entry in the BD tablepointing to an advertising node and it creates a L3 host route based onthe MAC and IP address in the route advertisement pointing to remoteVXLAN Tunnel Endpoint (VTEP) or MPLS PE with per MPLS or VXLAN VNIencapsulation 420. This results in BGP next hop address of egress PEalong with VPN MPLS label or VNI. The BGP route target of the IP-VRF isattached to the advertised route.

If the egress PE is the symmetric IRB PE, it will have the necessaryinformation to program forwarding to do the symmetric IRB action, whichreceives a packet with both Label1 and Label2 fields. If the receivingPE is an asymmetric IRB PE, the asymmetric IRB PE will ignore the Label2field and create a local ARP entry and local MAC entry.

If IP-VRF attributes are not present, indicating that it is anasymmetrically formatted route, the hybrid PE creates an ARP entry withthe IP and MAC route 406. Then it creates a local MAC entry in the MACtable 408. The PE imports L2 information in BD that maps to BD routetarget 410 and programs MAC entry in BD table pointing to advertisingnode. Then it creates an adjacency on the egress IRB interface for MACand IP 412. This results in BGP next hop address of egress PE along withVPN MPLS label or VNI. The BGP route target of the IP-VRF is attached tothe advertised route.

If the egress PE is a symmetric IRB PE, it receives a packet with bothLabel1 and Label2 fields, which means it has the same encoding as and isoperable with a symmetric IRB PE. For example, the symmetric IRB PE willimport the IP host route into the corresponding IP-VRF based on theIP-VRF route target and the MAC address into the local MAC-VRF based onthe MAC-VRF's route target. An asymmetric IRB PE would ignore the Label2field because the IP-VRF attributes are not recognized by an asymmetricIRB PE.

FIG. 5A illustrates the operation of a symmetric IRB PE 500. Generally,in a symmetric IRB PE 500, the ingress PE 502 performs an IP lookup inthe associated IP-VRF table. The lookup identifies BGP next hop ofegress PE 504 along with the encapsulation type and the associated MPLSor VNI values. The ingress PE 512 gets the destination MAC address forthe IP address from its ARP table and encapsulates the packet with thatdestination router MAC address and sends the packet its destinationsubnet.

In a symmetric IRB PE 500, an EVPN MAC and IP advertisement route isbuilt and advertised to the other PE's participating in the EVPN. TheMPLS Label2 field is set to either an MPLS label or a VNI correspondingto the tenant's IP-VRF. The inclusion of MPLS Label2 field signals tothe receiving PE that the route is for symmetric IRB mode. If thereceiving PE only supports asymmetric IRB mode, then the receiving PEmust ignore the Label2 field and install the MAC address in thecorresponding MAC-VRF and the IP and MAC address in the ARP table. Theforwarding is performed using the destination MAC address.

FIG. 5B illustrates the operation of an asymmetric IRB PE 510.Generally, in an asymmetric IRB PE 510, the ingress PE 512 performs anIP lookup in the associated IP-VRF table. The lookup identifies a localadjacency to the IRB interface associated with the egress PE's 514MAC-VRF and BT. The ingress PE 512 gets the destination MAC address forthe IP address from its ARP table and encapsulates the packet with thatdestination MAC address and sends the packet its destination subnet.

In an asymmetric IRB PE 510, an EVPN MAC and IP advertisement route isbuilt and advertised to the other PE's participating in the EVPN. Theroute must not include an MPLS Label2 field. When a PE that onlysupports symmetric mode receives this route, it only imports the MACaddress to the corresponding MAC-VRF table. A hybrid IRB PE would importthe IP and MAC route into the ARP table.

The embodiments may be implemented as firmware, hardware, and/orsoftware logic embodied in a tangible medium that, when executed, isoperable to perform the various methods and processes described above.That is, the logic may be embodied as physical arrangements, modules, orcomponents. A tangible medium may be any computer-readable medium thatis capable of storing logic or computer program code which may beexecuted, e.g., by a processor or an overall computing system, toperform methods and functions associated with the embodiments. Suchcomputer-readable mediums may include, but are not limited to including,physical storage and/or memory devices. Executable logic may include,but is not limited to including, code devices, computer program code,and/or executable computer commands or instructions.

Although a variety of examples and other information was used to explainaspects within the scope of the appended claims, no limitation of theclaims should be implied based on particular features or arrangements insuch examples, as one of ordinary skill would be able to use theseexamples to derive a wide variety of implementations. Further andalthough some subject matter may have been described in languagespecific to examples of structural features and/or method steps, it isto be understood that the subject matter defined in the appended claimsis not necessarily limited to these described features or acts. Forexample, such functionality can be distributed differently or performedin components other than those identified herein. Rather, the describedfeatures and steps are disclosed as examples of components of systemsand methods within the scope of the appended claims.

1. A method comprising: receiving an Ethernet Virtual Private Network(EVPN) MAC/IP Advertisement Route from a Provider Edge (PE) router;examining a Multiprotocol Label Switching (MPLS) label of the EVPNMAC/IP Advertisement Route; determining that Internet Protocol VirtualRoute Forwarding (IP-VRF) attributes are not carried in the MPLS labelof the EVPN MAC/IP Advertisement Route; adding, based on information inthe EVPN MAC/IP Advertisement Route, an Address Resolution Protocol(ARP) entry to an ARP table, the ARP entry including at least one of aMAC address and an IP address from the received the EVPN MAC/IPAdvertisement Route; and adding, in response to the determining thatIP-VRF attributes are not carried in the MPLS label, a MAC entry to aMAC table identified by a Border Gateway Protocol (BGP) target of theMAC address.
 2. The method of claim 1, further comprising: determiningthat Internet Protocol Virtual Route Forwarding (IP-VRF) attributes arecarried in the MPLS label of the EVPN MAC/IP Advertisement Route; andadding a host IP route with Virtual Route Forwarding (VRF) to an IP-VRFtable per Multiprotocol Label Switching (MPLS) label; and adding, inresponse to the determining that IP-VRF attributes are carried in theMPLS label, a MAC entry to a MAC table identified by a BGP target of theMAC address.
 3. The method of claim 2, wherein adding a host IP routewith Virtual Route Forwarding (VRF) to an IP-VRF table can be per VXLANNetwork Identifier (VNI) encapsulation.
 4. The method of claim 1,wherein the Ethernet Virtual Private Network (EVPN) MAC/IP AdvertisementRoute can have Layer 2 or Layer 3 information.
 5. The method of claim 1,wherein receiving an Ethernet Virtual Private Network (EVPN) MAC/IPAdvertisement Route occurs at an ingress switch.
 6. A Provider Edge (PE)system comprising: one or more processors; and a computer-readablestorage medium having stored therein instructions which, when executedby the one or more processors, cause the one or more processors toperform operations comprising: receiving an Ethernet Virtual PrivateNetwork (EVPN) MAC/IP Advertisement Route from a first PE router;determining that the EVPN MAC/IP Advertisement Route is associated withan asymmetric IRB mode based on a MPLS label of the EVPN MAC/IPAdvertisement Route; adding an Address Resolution Protocol (ARP) entryto an ARP table from information in the EVPN MAC/IP Advertisement Routethat includes both a MAC address and an IP address from the receivedroute; and adding a MAC entry to a MAC table identified by a BorderGateway Protocol (BGP) target of the MAC address.
 7. The Provider Edge(PE) system of claim 6, further comprising: determining that InternetProtocol Virtual Route Forwarding (IP-VRF) attributes are carried in theMPLS label of the Ethernet Virtual Private Network (EVPN) MAC/IPAdvertisement Route; and adding a host IP route with VRF to a IP-VRFtable per Multiprotocol Label Switching (MPLS) label; and adding a MACentry to a MAC table identified by a BGP target of the MAC address. 8.The Provider Edge (PE) system of claim 7, further comprising: building asecond Ethernet Virtual Private Network (EVPN) MAC/IP AdvertisementRoute from the information; and advertising the second EVPN MAC/IPAdvertisement Route to a second PE device.
 9. The Provider Edge (PE)system of claim 6, further comprising: building a second EthernetVirtual Private Network (EVPN) MAC/IP Advertisement Route from theinformation; and advertising the second EVPN MAC advertisement to asecond PE device.
 10. The Provider Edge (PE) device of claim 9, whereinthe advertising the second Ethernet Virtual Private Network (EVPN)MAC/IP Advertisement Route is advertised with two route targets, one forthe Media Access Control Virtual Route Forwarding (MAC-VRF) and one forInternet Protocol Virtual Route Forwarding (IP-VRF) when communicationis between different IP subnets.
 11. The Provider Edge (PE) system ofclaim 6, wherein the Ethernet Virtual Private Network (EVPN) MAC/IPAdvertisement Route can have Layer 2 or Layer 3 information.
 12. TheProvider Edge (PE) system of claim 6, wherein receiving an EthernetVirtual Private Network (EVPN) MAC/IP Advertisement Route occurs at aningress switch.
 13. The Provider Edge (PE) system of claim 6, whereinthe encapsulation is per VXLAN Network Identifier (VNI) rather than MPLSlabel.
 14. A non-transitory computer-readable storage medium havingstored therein instructions which, when executed by one or moreprocessors, cause the one or more processors to perform operationscomprising: receiving a route advertisement from a first Provider Edge(PE) router; determining that the EVPN MAC/IP Advertisement Route isasymmetric based on a lack of Internet Protocol Virtual Route Forwarding(IP-VRF) attributes associated with the route advertisement; andcreating forwarding information, based on the information in the EVPNMAC/IP Advertisement Route, to provide inter-subnet connectivity; andadvertising a second EVPN MAC/IP Advertisement Route with the forwardinginformation to a to a second PE router when communication is betweendifferent IP subnets.
 15. The non-transitory computer-readable storagemedium of claim 14, wherein creating forwarding information is based onthe information in the EVPN MAC/IP Advertisement Route, to provideinter-subnet connectivity comprises: adding an Address ResolutionProtocol (ARP) entry to an ARP table from information in the routeadvertisement that includes both the MAC address and the IP address fromthe received route, in response to the determining that IP-VRFattributes are not carried in the MPLS label; and adding a MAC entry toa MAC table identified by a Border Gateway Protocol (BGP) target of theMAC address, in response to the determining that IP-VRF attributes arenot carried in the MPLS label.
 16. The non-transitory computer-readablestorage medium of claim 14, wherein creating forwarding information,based on the information in the EVPN MAC/IP Advertisement Route, toprovide inter-subnet connectivity comprises: adding a host IP route withVirtual Route Forwarding (VRF) to a IP-VRF table per Multiprotocol LabelSwitching (MPLS) encapsulation, in response to the determining that IPVRF attributes are carried in the MPLS label; and adding a MAC entry toa MAC table identified by a BGP target of the MAC address in response tothe determining that IP-VRF attributes are carried in the MPLS label.17. The non-transitory computer-readable storage medium of claim 16,wherein adding a host IP route with Virtual Route Forwarding (VRF) to anIP-VRF table can be per VXLAN Network Identifier (VNI) encapsulation.18. The non-transitory computer-readable storage medium of claim 14,wherein the Ethernet Virtual Private Network (EVPN) MAC/IP AdvertisementRoute can have Layer 2 or Layer 3 information.
 19. The non-transitorycomputer-readable storage medium of claim 14, wherein receiving anEthernet Virtual Private Network (EVPN) MAC/IP Advertisement Routeoccurs at an ingress switch.
 20. The non-transitory computer-readablestorage medium of claim 14, wherein the second PE router could be anasymmetric IRB PE or a symmetric IRB PE.